Elimination of dead time effects in three phase inverters

In the design of inverters it is necessary to include a "dead time" in switching signals in order to avoid the simultaneous conduction of the devices on the same electrical trajectory or leg. Incorporation of this dead time produces a modification on commutation real angles with respect to the theoreticals. In this paper, an analysis and compensation of the dead time effects in three phase inverters is presented. It is shown that the dead time generates a decrease in the magnitude voltage of the harmonic fundamental and an increase in the low order harmonics. The paper also includes the implementation of a technique to compensate the dead time effect through the sensing current; this technique is applicable to sinusoidal and programmed PWM techniques. The analysis and compensation of the dead time are validated by means of experimental results in a three phase inverter for an induction motor drive, and a three phase inverter for UPS.